Gases, liquids, and other environmental factors may cause deterioration of various goods, such as food, medical, and electrical devices, pharmaceutical products. Thus, conventionally, barrier films have been included on or within the packaging associated with sensitive goods to prevent or limit the permeation of gases or liquids, such as oxygen and water, through the packaging during manufacturing, storage, or use of the goods.
Atomic layer deposition (ALD) is a thin film deposition process described in U.S. Pat. No. 8,137,464 of Dickey et al. (“the '464 patent”), filed Mar. 26, 2007 as U.S. application Ser. No. 11/691,421 and entitled Atomic Layer Deposition System and Method for Coating Flexible Substrates, and in U.S. Pat. No. 8,202,366 of Dickey et al. (“the '366 patent”), filed Apr. 6, 2010 as U.S. application Ser. No. 12/755,239 and entitled Atomic Layer Deposition System Utilizing Multiple Precursor Zones for Coating Flexible Substrates. Thin film deposition in accordance with the methods and systems disclosed in the '464 and '366 patents has been proposed for deposition of barrier films on flexible substrates for packaging for sensitive goods and other uses.
Conventional wisdom holds that nanolaminates make better barrier films than mixed materials. See, for example, U.S. Pat. No. 4,486,487 disclosing nanolaminates with Al2O3 and TiO2 layers and U.S. Pat. No. 7,294,360 disclosing nanolaminates with Al2O3 and SiO2 layers formed from trimethylaluminum (TMA, or Al2(CH3)6 (as a dimer)) and tris-(tert-butoxy)silanol. Complex multilayer barrier films including five or six pairs of alternating organic and inorganic layers have been used to prevent the permeation of oxygen and water through plastic substrates of organic light-emitting diodes (OLEDs). Some such barriers are so-called nanolaminates made by ALD, formed from discrete, individual layers typically having thicknesses under 10 nanometers (nm). However, multilayer barriers result in a relatively high overall barrier thickness that is not ideal for thin film flexible packaging. Moreover, thick film stacks may affect light transmission through the barrier film.
Applicants recognized that mixed AlTiO films may act as a moisture barrier (e.g., films having a thickness of less than approximately 3 or 4 nm may exhibit a water vapor transmission rate (WVTR) of less than 0.005 g/m2/day) and may exhibit a refractive index of approximately 1.8-1.9, as disclosed in U.S. application Ser. No. 13/546,930 (“the '930 application”), filed Jul. 11, 2012. While these films may be comparatively thinner than nanolaminate structures formed from alumina and titania, a need remains for barrier films having very low steady-state vapor permeability and very low optical transmission loss.